The present invention relates to novel quinozoline inhibitors of endothelin converting enzyme useful as pharmaceutical agents, to methods for their production, to pharmaceutical compositions which include these compounds and a pharmaceutically acceptable carrier, and to pharmaceutical methods of treatment. More particularly, the novel compounds of the present invention are inhibitors of endothelin converting enzyme useful in treating elevated levels of endothelin and in controlling hypertension, myocardial infarction and ischemia, metabolic, endocrinological, and neurological disorders, congestive heart failure, endotoxic and hemorrhagic shock, septic shock, subarachnoid hemorrhage, arrhythmias, asthma, acute and chronic renal failure, cyclosporin-A induced nephrotoxicity, angina, gastric mucosal damage, ischemic bowel disease, cancer, pulmonary hypertension, preeclampsia, atherosclerotic disorders including Raynaud's disease and restenosis, cerebral ischemia and vasospasm, and diabetes.
Endothelin-1 (ET-1), a potent vasoconstrictor, is a 21 amino acid bicyclic peptide that was first isolated from cultured porcine aortic endothelial cells. Endothelin-1, is one of a family of structurally similar bicyclic peptides which include; ET-2, ET-3, vasoactive intestinal contractor (VIC), and the sarafotoxins (SRTXs). The unique bicyclic structure and corresponding arrangement of the disulfide bridges of ET-1, which are the same for the endothelins, VIC, and the sarafotoxins, has led to significant speculation as to the importance of the resulting induced secondary structure to receptor binding and functional activity. ET-1 analogs with incorrect disulfide pairings exhibit at least 100-fold less vasoconstrictor activity.
Endothelin-1 is generated from a 203 amino acid peptide known as preproendothelin by an unknown dibasic endopeptidase. This enzyme cleaves the prepropeptide to a 38 (human) or 39 (porcine) amino acid peptide known as big endothelin or proendothelin. Big ET is then cleaved by an enzyme, known as endothelin converting enzyme or ECE, to afford the biologically active molecule ET-1. Big ET is only 1% as potent as ET-1 in inducing contractile activity in vascular strips but it is equally potent in vivo at raising blood pressure, presumably by rapid conversion to ET-1 (Kimura S, Kasuya Y, Sawamura T, et al., "Conversion of big endothelin-1 to 21-residue endothelin-1 is essential for expression of full vasoconstrictor activity: Structure-activity relationship of big endothelin-1," J Cardiovasc Pharmacol 1989;13:S5). There have been numerous reports describing possible proteases in both the cytoplasm and membrane bound cellular fractions of endothelial cells (Ikegawa R, Matsumura Y, Takaoka M, et al., "Evidence for pepstatin-sensitive conversion of porcine big endothelin-1 to endothelin-1 by the endothelial cell extract," Biochem Biophys Res Commun 1990;167:860; Sawamura T, Kimura S, Shinmi O, et al., "Characterization of endothelin converting enzyme activities in soluble fraction of bovine cultured endothelial cells," Biochem Biophys Res Commun 1990;169:1138; Sawamura T, Shinmi O, Kishi N, et al., "Analysis of big endothelin-1 digestion by cathepsin D." Biochem Biophys Res Commun 1990;172:883; Shields PP, Gonzales TA, Charles D, et al., "Accumulation of pepstatin in cultured endothelial cells and its effect on endothelin processing," Biochem Biophys Res Commun 1991;177:1006; Matsumura Y, Ikegawa R, Tsukahara Y, et al., "Conversion of big endothelin-1 to endothelin-1 by two types of metalloproteinases derived from porcine aortic endothelial cells," FEBS Lett, 1990;272:166; Sawamura T, Kasuya Y, Matsushita SN, et al., "Phosphoramidon inhibits the intracellular conversion of big endothelin-1 to endothelin-1 in cultured endothelial cells," Biochem Biophys Res Commun 1991;174:779; Takada J, Okada K, Ikenaga T, et al., "Phosphoramidon-sensitive endothelin-converting enzyme in the cytosol of cultured bovine endothelial cells," Biochem Biophys Res Commun 1991;176:860; Ahn K, Beningo K, Olds G, Hupe D, "Endothelin-converting enzyme from bovine and human endothelial cells," J Vasc Res 1991;29:76, 2nd International symposium on endothelium-derived vasoactive factors). Many groups have chosen to isolate ECE from endothelial cells of various species, since endothelin is known to be synthesized and secreted by this cell type. It was initially reported that two types of protease activity were present in porcine or bovine endothelial cells that could cause conversion of big ET to ET in vitro (Ikegawa R, supra; Sawamura T, supra; Matsumura Y, supra; Takada J, supra; Ahn K, supra). However, it was subsequently found that the aspartic protease activity from porcine endothelial cells, thought to be predominantly cathepsin D, also caused further degradation of ET-1 and was therefore unlikely to be the true ECE (Sawamura T, supra). Moreover, human cathepsin D also causes rapid degradation of ET-1. In addition, there has been one study showing that the intracellular accumulation of pepstatin, an aspartic protease inhibitor, did not inhibit ET-1 production in cultured bovine aortic endothelial cells (Shields PP, supra). Stronger evidence that ECE is in fact a neutral metalloprotease has appeared (Matsumura Y, supra; Sawamura T, supra; Takada J, supra; Ahn K, supra) and, recently, rat and bovine ECE genes have been cloned and expressed, confirming that ECE is a phosphoramidon sensitive metalloprotease. (Shimada, K., Tanzawa, K., J. Biol. Chem. 1994, 269, 18275) (Dong, X., Emoto, N., Giaid, A., Slaughter, C., Kaw, S., deWit, D., Yanagisawa, M., Cell 1994, 78, 1-20). However, the nonspecific metalloproteinase inhibitor, phosphoramidon, has been shown to inhibit the intracellular conversion of big ET-1 to ET-1 in cultured vascular endothelial cells and smooth muscle cells (Sawamura T, supra).
ET-converting activity has been detected in both the membranous and cytosolic fractions of cultured porcine, bovine, and human endothelial cells (Matsumura Y, supra). Micromolar concentrations of phosphoramidon have been shown to block the pressor response of big ET both in vitro and in vivo (Takada J, supra; Fukuroda T, Noguchi K, Tsuchida S, et al., "Inhibition of biological actions of big endothelin-1 by phosphoramidon," Biochem Biophys Res Commun 1990;172:390; Matsumura Y, Hisaki K, Takaoka M, Morimoto S, "Phosphoramidon, a metalloproteinase inhibitor, suppresses the hypertensive effect of big endothelin-1," Eur J Pharmacol 1990;185:103; McMahon EG, Palomo MA, Moore WM, et al., "Phosphoramidon blocks the pressor activity of porcine big endothelin-1-(1-39) in vivo and conversion of big endothelin-1-(1-39) to endothelin-1-(1-21) in vitro," Proc Natl Acad Sci USA 1991;88:703). It has recently been reported that phosphoramidon is able to inhibit vasoconstrictor effects evoked by intravenous injections of big ET-1 in anaesthetized pigs, but did not have any effect on the plasma ET-1 level (Modin A, Pernow J, Lundberg JM, "Phosphoramidon inhibits the vasoconstrictor effects evoked by big endothelin-1 but not the elevation of plasma endothelin-1 in vivo," Life Sci 1991;49:1619). It should be noted that phosphoramidon is a rather general metalloproteinase inhibitor and clearly the discovery of specific ECE inhibitors such as those described in the present invention is important.
The importance of ECE inhibitors is supported further by more recent reports. Several studies demonstrating the inhibition of ECE by metalloprotease inhibitors like phosphoramidon in vitro have been published (Doherty, A. D., Endothelin: A New Challenge. J. Med. Chem. 1992, 35, 1493; Simonson, J. S., Endothelins: Multifunctional Renal Peptides. Physiological Reviews. 1993, 73, 375; Opgenorth, T. J.; Wu-Wong, J. R.; Shiosaki, K. Endothelin Converting Enzymes, FASEB. J. 1992, 6, 2653-2659; Pollock, D. M.; Opgenorth, T. J. Evidence for metalloprotease involvement in the in vivo effects of big endothelin-1 Am. J. Physiol. 1991, 261, 257-263). These studies have also been followed up by in vivo studies where the effects Of ET in physiological conditions have been blocked by ECE inhibitors. For example, several reports have demonstrated that phosphoramidon (IC.sub.50 =.about.1 .mu.M) inhibits ECE in vitro. These results were supported by in vivo studies where phosphoramidon blocked the vasoconstrictive effects of ET. In ganglion-blocked anesthetized rats the pressor response of big ET-1 was blocked by phosphoramidon in a dose-dependent manner (McMahon, E. G.; Palomo, M. A.; Moore, W. M. Phosphoramidon blocks the pressor activity of big endothelin (1-39) and lowers blood pressure in spontaneously hypertensive rats. J. Cardiovasc, Pharmacol. 1991, 17 (Suppl. 17), S29-S33; McMahon, E. G.; Palomo, M. A.; Moore, W. M.; McDonald, J. F.; Stern, M. K. Phosphoramidon blocks the pressor activity of porcine big endothelin-1-(1-39) in vivo and conversion of big endothelin-1-(1-39) to endothelin-1-(1-21) in vitro Proc. Natl. Acad. Sci (USA), 1991, 88, 703-707). Phosphoramidon was also shown to inhibit the effects of big ET-1 in the microvasculature of anesthetized hamsters and has also been used to suppress the lethality induced by the intravenous infusion of big ET-1 (Lawerence, E.; Brain, S. D. Big endothelin-1 and big endothelin-3 are constrictor agents in the microvasculature: evidence for the local phosphoramidon-sensitive conversion of big endothelin-1. Eur. J. Pharmacol. 1993, 233, 243-250). In all cases it was shown that phosphoramidon inhibited the effects of big ET-1 and not ET-1 indicating that it was not behaving as a receptor antagonist. Intracisternal administration of big ET-1 in anesthetized dogs decreased the caliber of the basilar artery on the angiogram and systemic arterial pressure was also elevated. These effects were blocked by phosphoramidon (Shinyama, H.; Uchida, T.; Kido, H.; Hayashi, K.; Watanabe, M.; Matsumura, Y.; Ikegawa, R.; Takaoka, M.; Morimoto, S. Phosphoramidon inhibits the conversion of intracisternally administered big endothelin-1 to endothelin-1. Biochem Biophys Res Commun 1991, 178, 24-30). Similar enzyme inhibitory activity has been reported in the studies involving phosphoramidon sensitive inhibition of hemodynamic actions of big ET-1 in rat brain (Hashim, M. A.; Tadepalli. Functional evidence for the presence of a phosphoramidon-sensitive enzyme in rat brain that converts big endothelin-1 to endothelin-1. Life Sci. 1991, 49, 207-211).
Endothelin is involved in many human disease states.
Several in vivo studies with ET antibodies have been reported in disease models. Left coronary artery ligation and reperfusion to induce myocardial infarction in the rat heart, caused a four- to sevenfold increase in endogenous endothelin levels. Administration of ET antibody was reported to reduce the size of the infarction in a dose-dependent manner (Watanabe T, et al., "Endothelin in Myocardial Infarction," Nature (Lond.) 1990;344:114). Thus, ET may be involved in the pathogenesis of congestive heart failure and myocardial ischemia (Margulies KB, et al., "Increased Endothelin in Experimental Heart Failure," Circulation 1990;82:2226).
Studies by Kon and colleagues using anti-ET antibodies in an ischemic kidney model, to deactivate endogenous ET, indicated the peptide's involvement in acute renal ischemic injury (Kon V, et al., "Glomerular Actions of Endothelin In vivo," J Clin Invest 1989;83:1762). In isolated kidneys, preexposed to specific antiendothelin antibody and then challenged with cyclosporine, the renal perfusate flow and glomerular filtration rate increased, while renal resistance decreased as compared with isolated kidneys preexposed to a nonimmunized rabbit serum. The effectiveness and specificity of the anti-ET antibody were confirmed by its capacity to prevent renal deterioration caused by a single bolus dose (150 pmol) of synthetic ET, but not by infusion of angiotensin II, norepinephrine, or the thromboxane A.sub.2 mimetic U-46619 in isolated kidneys (Perico N, et al., "Endothelin Mediates the Renal Vasoconstriction Induced by Cyclosporine in the Rat," J Am Soc Nephrol 1990;1:76).
Others have reported inhibition of ET-1 or ET-2-induced vasoconstriction in rat isolated thoracic aorta using a monoclonal antibody to ET-1 (Koshi T, et al., "Inhibition of Endothelin (ET)-1 and ET-2-Induced Vasoconstriction by Anti-ET-1 Monoclonal Antibody," Chem Pharm Bull 1991;39:1295).
Combined administration of ET-1 and ET-1 antibody to rabbits showed significant inhibition of the blood pressure and renal blood flow responses (Miyamori I, et al., Systemic and Regional Effects of Endothelin in Rabbits: Effects of Endothelin Antibody," Clin Exp. Pharmacol. Physiol 1990;17:691).
Other investigators have reported that infusion of ET-specific antibodies into spontaneously hypertensive rats (SHR) decreased mean arterial pressure (MAP), and increased glomerular filtration rate and renal blood flow. In the control study with normotensive Wistar-Kyoto rats (WKY), there were no significant changes in these parameters (Ohno A, "Effects of Endothelin-Specific Antibodies and Endothelin in Spontaneously Hypertensive Rats," J Tokyo Women's Med Coll 1991;61:951).
In addition, elevated levels of endothelin have been reported in several disease states (see Table I below).
TABLE 1 ______________________________________ Plasma Concentrations of ET-1 in Humans ET Plasma Normal Levels Condition Reported Condition (pg/mL) ______________________________________ Atherosclerosis 1.4 3.1 pmol/L Surgical operation 1.5 7.3 Buerger's disease 1.6 4.8 Takayasu's arteries 1.6 5.3 Cardiogenic shock 0.3 3.7 Congestive heart failure 9.7 20.4 (CHF) Mild CHF 7.1 11.1 Severe CHF 7.1 13.8 Dilated Cardiomyopathy 1.6 7.1 Preeclampsia 10.4 pmol/L 22.6 pmol/L Pulmonary hypertension 1.45 3.5 Acute myocardial 1.5 3.3 infarction (several reports) 6.0 11.0 0.76 4.95 0.50 3.8 Subarachnoid hemorrhage 0.4 2.2 Crohn's disease 0-24 Fmol/mg 4-64 Fmol/mg Ulcerative colitis 0-24 Fmol/mg 20-50 Fmol/mg Cold pressor test 1.2 8.4 Raynaud's phenomenon 1.7 5.3 Raynaud's/hand cooling 2.8 5.0 Hemodialysis &lt;7 10.9 (several reports) 1.88 4.59 Chronic renal failure 1.88 10.1 Acute renal failure 1.5 10.4 Uremia before 0.96 1.49 hemodialysis Uremia after 0.96 2.19 hemodialysis Essential hypertension 18.5 33.9 Sepsis syndrome 6.1 19.9 Postoperative cardiac 6.1 11.9 Inflammatory arthritides 1.5 4.2 Malignant 4.3 16.2 hemangioendothelioma (after removal) ______________________________________
Burnett and co-workers recently demonstrated that exogenous infusion of ET (2.5 ng/kg/mL) to anesthetized dogs, producing a doubling of the circulating concentration, did have biological actions (Lerman A, et al., "Endothelin Has Biological Actions at Pathophysiological Concentrations," Circulation 1991;83:1808). Thus heart rate and cardiac output decreased in association with increased renal and systemic vascular resistances and antinatriuresis. These studies support a role for endothelin in the regulation of cardiovascular, renal, and endocrine function.
In the anesthetized dog with congestive heart failure, a significant two- to threefold elevation of circulating ET levels has been reported (Cavero PG, et al., "Endothelin in Experimental Congestive Heart Failure in the Anesthetized Dog," Am J Physiol 1990;259:F312), and studies in humans have shown similar increases (Rodeheffer RJ, et al., "Circulating Plasma Endothelin Correlates With the Severity of Congestive Heart Failure in Humans," Am J Hypertension 1991;4:9A). When ET was chronically infused into male rats, to determine whether a long-term increase in circulating ET levels would cause a sustained elevation in mean arterial blood pressure, significant, sustained, and dose-dependent increases in mean arterial blood pressure were observed. Similar results were observed with ET-3 although larger doses were required (Mortenson LH, et al., "Chronic Hypertension Produced by Infusion of Endothelin in Rats," Hypertension 1990;15:729). Recently the nonpeptide endothelin antagonist RO 46-2005 has been reported to be effective in models of acute renal ischemia and subarachnoid hemorrhage in rats (3rd International Conference on Endothelin, Houston, Tex., February 1993). In addition, the ET.sub.A antagonist BQ-153 has also been shown to prevent early cerebral vasospasm following subarachnoid hemorrhage after intracisternal injection (Clozel M., et al., Life Sciences 1993;52:825); to prevent blood pressure increases in stroke-prone spontaneously hypertensive rats (Nishikibe M, et al., Life Sciences 1993;52:717); and to attenuate the renal vascular effects of ET-1 in anaesthetized pigs (Cirino M, et al., J Pharm Pharmacol 1992;44:782).
Plasma endothelin-1 levels were dramatically increased in a patient with malignant hemangio-endothelioma (Nakagawa K, et al., Nippon Hifuka Gakkai Zasshi 1990;100:1453).
The ET receptor antagonist BQ-123 has been shown to block ET-1-induced bronchoconstriction and tracheal smooth muscle contraction in allergic sheep providing evidence for expected efficacy in bronchopulmonary diseases such as asthma (Noguchi, et al., Am Rev Respir Dis 1992;145(4 Part 2):A858).
Circulating endothelin levels are elevated in women with preeclampsia and correlate closely with serum uric acid levels and measures of renal dysfunction. These observations indicate a role for ET in renal constriction in preeclampsia (Clark BA, et al., Am J Obstet Gynecol 1992;166:962).
Plasma immunoreactive endothelin-1 concentrations are elevated in patients with sepsis and correlate with the degree of illness and depression of cardiac output (Pittett J, et al., Ann Surg 1991;213(3):261).
In addition, the ET-1 antagonist BQ-123 has been evaluated in a mouse model of endotoxic shock. This ET.sub.A antagonist significantly increased the survival rate in this model (Toshiaki M, et al., 20.12.90. EP 0 436 189 A1).
Endothelin is a potent agonist in the liver eliciting both sustained vasoconstriction of the hepatic vasculature and a significant increase in hepatic glucose output (Gandhi CB, et al., J. Biol. Chem. 1990;265(29):17432). In streptozotocin-diabetic rats, there is an increased sensitivity to endothelin-1 (Tammesild PJ, et al., Clin Exp Pharmacol Physiol 1992;19(4):261). In addition, increased levels of plasma ET-1 have been observed in microalbuminuric insulin-dependent diabetes mellitus patients indicating a role for ET in endocrine disorders such as diabetes (Collier A, et al., Diabetes Care 1992;15(8):1038).
ET.sub.A antagonist receptor blockade has been found to produce an antihypertensive effect in normal to low renin models of hypertension with a time course similar to the inhibition of ET-1 pressor responses (Basil MK, et al., J Hypertension 1992;10(Suppl 4):S49). The endothelins have been shown to be arrhythmogenic, and to have positive chronotropic and inotropic effects, thus ET receptor blockade would be expected to be useful in arrhythmia and other cardiovascular disorders (Han S-P, et al., Life Sci 1990;46:767).
The widespread localization of the endothelins and their receptors in the central nervous system and cerebrovascular circulation has been described (Nikolov RK, et al., Drugs of Today 1992;28(5):303). Intracerebroventricular administration of ET-1 in rats has been shown to evoke behavioral effects. These factors strongly suggest a role for the ETs in neurological disorders. The potent vasoconstrictor action of ETs on isolated cerebral arterioles suggests the importance of these peptides in the regulation of cerebrovascular tone. Increased ET levels have been reported in some CNS disorders, i.e., in the CSF of patients with subarachnoid hemorrhage and in the plasma of women with preeclampsia. Stimulation with ET-3 under conditions of hypoglycemia have been shown to accelerate the development of striatal damage as a result of an influx of extracellular calcium. Circulating or locally produced ET has been suggested to contribute to regulation of brain fluid balance through effects on the choroid plexus and CSF production. ET-1-induced lesion development in a new model of local ischemia in the brain has been described.
Circulating and tissue endothelin immunoreactivity is increased more than twofold in patients with advanced atherosclerosis (Lerman A., et al., New England J Med 1991;325:997). Increased endothelin immunoreactivity has also been associated with Buerger's disease (Kanno K, et al., J Amer Med Assoc 1990;264 2868) and Raynaud's phenomenon (Zamora MR, et al., Lancet 1990;336:1144). Likewise, increased endothelin concentrations were observed in hyper-cholesterolemic rats (Horio T, et al., Atherosclerosis 1991;89:239).
An increase of circulating endothelin levels was observed in patients that underwent percutaneous transluminal coronary angioplasty (PTCA) (Tahara A, et al., Metab Clin Exp 1991;40:1235; Sanjay K, et al., Circulation 1991;84(Suppl. 4):726).
Increased plasma levels of endothelin have been measured in rats (Stelzner TJ, et al., Am J Physiol 1992;262:L614) and humans (Miyauchi T, et al., Jpn J Pharmacol 1992;58:279P; Stewart DJ, et al., Ann Internal Medicine 1991;114:464) with pulmonary hypertension.
Elevated levels of endothelin have also been measured in patients suffering form ischemic heart disease (Yasuda M, et al., Amer Heart J 1990;119:801; Ray SG, et al., Br Heart J 1992;67:383) and either stable or unstable angina (Stewart JT, et al., Br Heart J 1991;66:7).
Infusion of an endothelin antibody 1 hour prior to and 1 hour after a 60-minute period of renal ischemia resulting in changes in renal function versus control. In addition, an increase in glomerular platelet-activating factor was attributed to endothelin (Lopez-Farre A, et al., J Physiology 1991;444:513-). In patients with chronic renal failure as well as in patients on regular hemodialysis treatment mean plasma endothelin levels were significantly increased (Stockenhuber F, et al., Clin Sci (Lond.) 1992;82:255). In addition, it has been suggested that the proliferative effect of endothelin on mesangial cells may be a contributing factor in chronic renal failure (Schultz PJ, J Lab Clin Med 1992;119:448).
Also, Haleen, S., et al., FASEB J. April 1994, demonstrated efficacy of an ET.sub.A /ET.sub.B antagonist, PD 145065, which essentially also blocks all ET function (similar to an ECE inhibitor) in a severe model of acute renal failure.
The effects of endothelin receptor blockade on ischemia-induced acute renal failure and mortality were assessed in rats undergoing unilateral nephrectomy and global ischemia in the remaining kidney. Sprague Dawley male rats (300-400 g) were housed in metabolic cages for 2 days before and 7 days after renal injury; urine output and plasma creatinine levels were monitored daily. On the day of renal injury, rats were anesthetized with sodium pentobarbital (50 mg/kg, IP), heparinized (50 units, IV), and instrumented with a tail vein canulae for drug or vehicle infusion. Both kidneys were exposed via a flank incision and the right kidney was removed. The left renal artery was clamped for 60 minutes and released. PD 145065 was infused 60 minutes prior to and following the ischemic period. Renal injury was evident 1 and 2 days following ischemia from a tenfold increase in plasma creatinine levels and significant decreases in urine output. Mortality occurred primarily between the second and third days post-injury. However, mortality was significantly less (52%, N=23) in rats treated with PD 145065 compared to vehicle rats (83%, N-23). In addition, urine output on the second day following renal injury was significantly different between treatment groups on either the first or second days post-injury. Thus blockade of endothelin receptors with PD 145065 significantly decreases mortality in rats subjected to ischemia-induced renal failure.
Local intra-arterial administration of endothelin has been shown to induce small intestinal mucosal damage in rats in a dose-dependent manner (Mirua S, et al., Digestion 1991;48:163). Administration of endothelin-1 in the range of 50-500 pmol/kg into the left gastric artery increased the tissue type plasminogen activator release and platelet activating formation and induced gastric mucosal hemorrhagic change in a dose-dependent manner (Kurose I, et al., Gut 1992;33:868). Furthermore, it has been shown that an anti-ET-1 antibody reduced ethanol-induced vasoconstriction in a concentration-dependent manner (Masuda E, et al., Am J Physiol 1992;262:G785). Elevated endothelin levels have been observed in patients suffering from Crohn's disease and ulcerative colitis (Murch SR, et al., Lancet 1992;339:381).
Additionally, there is a correlation between the inhibition of ECE in an in vitro assay, as used and described for the quinazolines of the present invention, and demonstration of in vivo activity in various pathophysiological conditions. For example, Grover, G. J., et al., J. Pharmacol. Exp. Ther. 1992, 263, 1074-1082, tested the effect of phosphoramidon, an ECE inhibitor, in a rat model of ischemia. Thus, Grover, G. J., et al. determined the effect of endothelin-1 (ET-1) and big ET-1 on coronary flow and contractile function in isolated nonischemic and ischemic rat hearts. Both ET-1 (IC.sub.50 =12 pMol) and big ET-1 (IC.sub.50 =2 nMol) reduced coronary flow in a concentration-dependent manner. Both 30 pMol ET-1 and 10 nMol big ET-1 pretreatment significantly reduced the time to contracture in globally ischemic rat hearts, suggesting a proischemic effect. Phosphoramidon (IC.sub.50 =100 .mu.M) and BQ-123 (0.3 .mu.M, ET.sub.A receptor antagonist) abolished the preischemic increase in coronary perfusion pressure induced by big ET-1 as well as its proischemic effect. Phosphoramidon was also given IV to rats subjected to coronary occlusion and reperfusion and was found to significantly reduce infarct size 24 hour postischemia. Phosphoramidon has been disclosed to be an effective inhibitor of ECE, IC.sub.50 =1 .mu.M, (European Published Patent Application EP 0518299 A2 and International Published Patent Application WO 92/13944).
Depending on the nature of substituent(s) attached, quinazolines have been described, for example, as fungicides, insecticides, bronchodilators, hypotensive agents, analgesics and active against the trachoma virus. See, e.g., German Patents 1,800,709, 4,208,254, U.K. Patent Specification 1,199,768, U.S. Pat. Nos. 3,184,462, 3,340,260, U.K. Patent 857,362, Patterson, S. E., et al., J. Heterocycl. Chem. (1992), 29(4), 703-6, Brown, D. J., et al., Aust. J. Chem. (1985), 38(3), 467-74, Genther, C. S., et al., J. Med. Chem. (1977), 20(2), 237-43, and Russian Patent SU-466,233. Also, European Patent Publication No. 0579496A1 describes 4-aminoquinazolines having inhibitory effect on cGMP-PDE, or additionally on TXA.sub.2 synthetase. The inhibition of cGMP-PDE is considered to be useful in diseases induced by enhancement of the metabolism of cGMP, such as hypertension, heart failure, myocardial infarction, angina, atherosclerosis, cardiac edema, pulmonary hypertension, renal insufficiency, nephrotic edema, hepatis edema, asthma, bronchitis, dementia, and immunodeficiency. The inhibition of thromboxane A.sub.2 (TXA.sub.2) synthetase is said to be useful for inflammation, hypertension, thrombosis, arteriosclerosis, cerebral apoplexy, asthma, myocardial infarction, cardiostenosis and cerebral infarction.
It has now been discovered that certain known and novel quinazoline derivatives possess a new property not previously reported for this class of compounds, which are inhibitors of endothelin converting enzyme. The quinazoline compounds of the present invention are thus useful in treating diseases associated with elevated levels of endothelin as mentioned above.